Bytecode parity by youknowone · Pull Request #7535 · RustPython/RustPython

… genexpr StopIteration wrapper

- split_blocks_at_jumps: split blocks at branch points so each has one exit
- jump_threading: thread jumps through single-jump blocks (flowgraph.c jump_thread)
- Backward conditional jump normalization: invert and create NOT_TAKEN+JUMP block
- Follow empty blocks in jump-to-return optimization (next_nonempty_block)
- Add PEP 479 StopIteration handler to compile_comprehension for generators

- Add Slice variant to ConstantData and BorrowedConstant
- Fold constant slices (x[:3], x[1:4]) into LOAD_CONST(slice(...))
- Marshal serialization/deserialization for Slice type
- Box::leak in borrow_obj_constant for PySlice roundtrip

Add Frozenset to ConstantData, BorrowedConstant, and marshal support.
Actual frozenset folding (BUILD_SET + CONTAINS_OP → LOAD_CONST frozenset)
requires VirtualMachine for element hashing and is deferred.